Observational Validation of Cutoff Models as Boundaries of Solar Proton Event Impact Area

High energy protons accelerated during solar proton events (SPEs) can access the Earth's middle atmosphere at high and middle latitudes causing large‐scale ionization and chemical changes. In this study, we have compared the performance of two cutoff latitude models that predict the limit of the SPE impact area in the atmosphere during 73 SPEs from 1997 to 2010. We use observations from 13 riometer stations and the D Region Absorption Prediction (DRAP) model to test the performance of the two cutoff latitude models by Dmitriev et al. (2010, https://doi.org/10.1029/2010JA015380) and Nesse Tyssøy and Stadsnes (2015, https://doi.org/10.1002/2014JA020508). We find similar performance from the two cutoff latitude models with respect to observations, but the Dmitriev et al. (2010, https://doi.org/10.1029/2010JA015380) model performs slightly better when observations are contrasted with the DRAP model results. The better performing model is also continuous with magnetic local time and particle energy, making it more suited for future use in climate model proton forcing. SPE forcing is currently included in climate models with a single static cutoff latitude limit at 60° geomagnetic latitude. In reality, the area that the solar protons can access is not static but varies with particle rigidity and geomagnetic conditions. We estimate that the SPE impact area is overestimated 90% of the time by this single static cutoff limit and the average overestimation of the impact area is about 15–25% for protons with energies <32 MeV

Appearance and Precipitation Characteristics of High-Latitude Pulsating Aurora

Characteristics of pulsating aurora (PsA) at the equatorward part of the auroral oval have been well described in the literature by previous studies. We extend our knowledge on high-latitude PsA observations by analysing 68 PsA events from the optical observatory on Svalbard, at 75 degrees magnetic latitude. We found that the pulsating emission structures are particularly large and transient, they do not experience drift motion, or their drift motion cannot be traced. Our results show that the high-latitude PsA events relate to lower geomagnetic activity and weaker solar wind driving than the lower latitude PsA. The high-latitude PsA events also occur less frequently, which is in agreement with their association to lower-than-average geomagnetic activity. We further show that the ionospheric electron density values during high-latitude PsA events are low compared to the lower latitude PsA. This, together with the non-traceable nature of the pulsating emission structures, suggests that these events are strongly dominated by a sub-type called Amorphous Pulsating Aurora (APA). We therefore conclude that, unlike the lower latitude PsA events, the high-latitude PsA events are not likely to cause direct changes in the chemical composition of the mesosphere.Peer reviewe

Appearance and Precipitation Characteristics of High-Latitude Pulsating Aurora

Characteristics of pulsating aurora (PsA) at the equatorward part of the auroral oval have been well described in the literature by previous studies. We extend our knowledge on high-latitude PsA observations by analysing 68 PsA events from the optical observatory on Svalbard, at 75° magnetic latitude. We found that the pulsating emission structures are particularly large and transient, they do not experience drift motion, or their drift motion cannot be traced. Our results show that the high-latitude PsA events relate to lower geomagnetic activity and weaker solar wind driving than the lower latitude PsA. The high-latitude PsA events also occur less frequently, which is in agreement with their association to lower-than-average geomagnetic activity. We further show that the ionospheric electron density values during high-latitude PsA events are low compared to the lower latitude PsA. This, together with the non-traceable nature of the pulsating emission structures, suggests that these events are strongly dominated by a sub-type called Amorphous Pulsating Aurora (APA). We therefore conclude that, unlike the lower latitude PsA events, the high-latitude PsA events are not likely to cause direct changes in the chemical composition of the mesosphere

Statistical study of auroral omega bands

The presence of very few statistical studies on auroral omega bands motivated us to test-use a semi-automatic method for identifying large-scale undulations of the diffuse aurora boundary and to investigate their occurrence. Five identical all-sky cameras with overlapping fields of view provided data for 438 auroral omega-like structures over Fennoscandian Lapland from 1996 to 2007. The results from this set of omega band events agree remarkably well with previous observations of omega band occurrence in magnetic local time (MLT), lifetime, location between the region 1 and 2 field-aligned currents, as well as current density estimates. The average peak emission height of omega forms corresponds to the estimated precipitation energies of a few keV, which experienced no significant change during the events. Analysis of both local and global magnetic indices demonstrates that omega bands are observed during substorm expansion and recovery phases that are more intense than average substorm expansion and recovery phases in the same region. The omega occurrence with respect to the substorm expansion and recovery phases is in a very good agreement with an earlier observed distribution of fast earthward flows in the plasma sheet during expansion and recovery phases. These findings support the theory that omegas are produced by fast earthward flows and auroral streamers, despite the rarity of good conjugate observations

Significance of drill & blast planning to decrease nitrogen residues of underground mining in Kittilä mine

Kittilän kaivos on vuoden 2016 malmin tuotantomääriltään Euroopan suurin maanalainen kultakaivos. Kaivoksen tuotantolouhinnassa käytetään elektronisia nalleja sekä räjähdysaineena Forcit Oy Ab valmistamaa Kemiitti 810 emulsioräjähdysainetta. Tässä diplomityössä tutkittiin maanalaisesta tuotantolouhinnasta aiheutuvia malmiin jääneitä typpipäästöjä. Tutkimuksen tavoitteena oli selvittää kuinka paljon räjähdysainetta jää reagoimatta louhosräjäytyksissä ja kuinka paljon louhe sisältää typpeä. Arvioitavina tekijöinä tutkittiin myös onko nousun tyypillä ja panostussukan käytöllä vaikutuksia louhinnan aiheuttamiin typpipäästöihin. Työn kirjallisuusosiossa esitellään louhinnasta aiheutuvan typen kulkeutuminen räjähdysaineesta ympäristöön ja räjähteen epätäydelliseen reagoimiseen oleellisesti vaikuttavat tekijät maanalaisessa tuotantolouhinnassa. Tämän lisäksi Kittilän kaivoksella käytetyt poraus- ja panostussuunnittelun pääperiaatteet esitellään louhostutkimusta pohjustavana tietona. Kokeellisessa tutkimuksessa kolmen testilouhoksen louhosräjäytyksistä kerätyille mobiilimurskatuille louhenäytteille suoritettiin laboratoriossa toteutetut liuotusanalyysit typpipitoisuuden selville saamiseksi. Virhelähteiden havaitsemiseksi louhoksien porarei’ille suoritettiin reikäsuoruusmittaukset, räjäytyksien tärinät mitattiin sekä louhituista tiloista laadittiin laserskannausmallit. Myös porauksen ja panostuksen raportoinnit sekä räjähdysaineen kaasuuntuminen dokumentoitiin. Kokeellisen tutkimuksen liuotusanalyysien mukaan testilouhoksien keskimääräisen louheen typpipitoisuus oli 38,0 g/t ja todellisella ominaispanostusasteella laskettaessa noin 30 % räjähdysaineesta jäi reagoimatta. Tutkimuksessa toteutettujen näytteenottomenetelmien raekoon valikoitumisen vuoksi tutkimuksessa saatujen tuloksien voidaan pitää liioittelevina, mutta louhoksien keskinäistä vertailua varten vähintään suuntaa antavina. Tuloksien perusteella voidaan päätellä että kiertoporattuja avausreikiä hyödyntävällä nousun tyypillä saavutetaan alhaisemmat louhinnan aiheuttamat typpipäästöt kuin tavanomaisella pitkäreikänousulla. Panostussukan käytön vaikutuksista ei tutkimuksessa saatu riittävän selkeitä tuloksia, jotta sen merkityksestä typpipäästöihin voitaisiin tehdä johtopäätöksiä. Panostussukan voi silti nähdä panostusta hyödyttävänä apuvälineenä estämässä räjähdysaineen vuotamisen porareiän mahdollisiin rakoihin heikkousvyöhykkeillä.Kittilä Mine is the largest underground gold mine in Europe as measured by the ore production in year 2016. The stoping method mainly used at the mine is transverse benchstoping with delayed backfill. In Kittilä mine, electronic detonators and Kemiitti 810 bulk-emulsion explosives are used in the production. This Master’s Thesis focused on nitrogen residues in blasted ore caused by underground stoping. The objective of the study was to find out how much explosives are not detonated correctly and how much nitrogen appear in blasted ore. In addition the target was to find out if the opening method of the stope and the utilization of blasting socks affects the levels of nitrogen residues. The literature review represents the fractions and flows of nitrogen from explosives to the environment and demonstrates the main factors influencing the incident of the detonation. Also the principles of drill & blast planning used at the mine is presented for prefacing the experimental part of the study. In the experimental study, dissolution analyses were performed for crushed ore samples from three individual stopes. To observe sources of errors, drill hole deviations, blasting vibrations and laser scans of the blasted stopes were implemented. Furthermore drilling and blasting reports along with sensitizing tests of the explosives were documented. According to the results of dissolution analyses, the average total nitrogen content of test stopes was 38 g/t and approximately 30 % of used explosives detonated incorrectly. However, because of the occurred decreasing of particle sizes due to sampling methods, the results can be considered overestimating the nitrogen amounts. Nevertheless the results are approximate for evaluating factors of the study. Concluding the study, the opening method with raise bored opening holes shows potential to decrease nitrogen residues of blasting compared to the conventional long hole raise. The results of utilizing blasting socks were insufficiently reliable to show their connection to nitrogen residues. Blasting socks though can be considered as auxiliary blasting equipment to prevent the spillage of explosives in drill holes located in fracture zones

Substorm occurrence during quiet solar wind driving

Peer reviewe

Automatic segmentation and classification of seven-segment display digits on auroral images

In this paper we describe a new and fully automatic method for segmenting and classifying digits in seven-segment displays. The method is applied to a dataset consisting of about 7 million auroral all-sky images taken during the time period of 1973–1997 at camera stations centred around Sodankylä observatory in northern Finland. In each image there is a clock display for the date and time together with the reflection of the whole night sky through a spherical mirror. The digitised film images of the night sky contain valuable scientific information but are impractical to use without an automatic method for extracting the date–time from the display. We describe the implementation and the results of such a method in detail in this pape